Hello John,
Gold plating all top and bottom layer traces might help sell it anyways. Glitz is important and the more expensive it is, the more hip it is going to be.
Might add a vibration compensation super duper gold cap, too. Must look very impressive but doesn't need to be connected to anything.
Regards, Joerg
On Sat, 12 Nov 2005 17:50:42 -0800, John Larkin
I wonder how much distortion do ceramic caps produce by reacting to the stress produced by their own internal electrical fields that are set up by the signal itself.
I agree that crystals are prone to vibration problems.
I am surprised that springs solved your problem. Many times a spring will merely change the frequency of the mechanical resonance. It's better to eliminate the resonance entirely by more firm mounting, or if that is impractical, use a vibration dampening material. Sometimes just moving the component to a place on the pcb that is less disturbed by vibration (close to a mounting screw) is good enough. Then you'd run sweeps on an electrodymaic shaker to prove the fix.
Vibration induced piezolectric noise from capacitors is a well-known problem. Ref: Linear Tech AN83, page 14:
"A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced FigureÊ B4?s trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise."
I think it all depends on how "quiet" is "quiet" for your application. Some people can accept hissy, buzzy audio, and others know that things can be made quieter.
mw
That story is some kind of deceitful ruse, no such thing occurred...
What if the "tapping" is caused by environmental factors, such as road vibration, acoustic waves from loudspeakers? Do you just stop the vehicle by the side of the road? Tell the musicians using your amplifier at the concert to stop playing so loudly?
Sounds like your NMR machine must be a large heavy device, mounted in a quiet building somewhere. No worries, then.
Maybe you missed my earlier post:
Ref: Linear Tech AN83, page 14:
"A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced FigureÊ B4?s trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise."
I'm trying to be helpful.
mw
Holy crap! I had exactly the same problem with a Vectron VS700
155.52MHz VCXO. Only I used an SMA connector for the test points :) Stress on the board would pull the oscillator frequency.My fix was to ignore the problem, as that level of stress only happened during testing.
Regards, Allan
In article , Boris Mohar wrote: [...]
The ceramic caps that have a microphonics problem are already non-linear for other reasons. The high K ceramics have both issues. NPO/COG don't. If a signal voltage is to be developed, it is best to use NPO capacitors in that part of the design.
No decent audio designer wil use ceramic caps in signal paths other than NPO/COG types.
Medium and Hi-K dielectrics are well known to distort the signal.
Graham
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by
How do you make filters with zero AC voltage across caps? :-)
You're kidding me right ?
Non-linearities in feedback loops can be amplified !
A least, that certainly applies to noise. Cue an unforgettable repair moment when a noisy transitor amp stage was discovered to be due to a defective C-E capacitor.
Anyway, the reason that med and hi-K caps distort is due to a non-linear coefficient of capacitance with applied voltage. And ceramics aren't normally used for coupling. I'm thinking of EQ applications for example.
Oh, I've measured that. Electrolytics used for coupling that have greater than ~
100 mV A.C. across them generate some weird products. It's not especially low-level either. The trick is to *never* have that much voltage there. I.e. use big caps. Using the 'bipolar' versions doesn't help either despite much common belief to the contrary.Graham
Digital!
But seriously, some ceramic caps have a nonlinear voltage/capacitance curve, so if you use them in filters where harmonic generation might be an issue, just keep the signal level low relative to the cap rated voltage. Or test the damned things.
High-voltage nonlinear transmission lines (shock/soliton lines) have been made with ceramic caps as the nonlinear elements.
John
You're kidding me, right?
John
You don't believe that crystal oscillators are shock/acceleration sensitive? You think we designed and fabbed these springs to trash Vectron stock?
OK, I admit it all.
John
Geez, don't tell Fred!
I don't think it's Vectron especially; all XOs are shock/acceleration sensitive to various extents. SC-cuts are supposed to be better, at roughly 3-5x the price.
After we spring-mounted the cans, you could whack the board all you wanted with no effect; I recall that the spring-mass mechanical resonance was in the 15 Hz range maybe, enough to lowpass filter the shocks pretty well, enough for the pll to track easily. But just the delicate touch of a small screwdriver against the can would make us lose lock for some milliseconds.
This is a very dumb pll, using a single EclipsLite flipflop as a bang-bang phase detector, so it wasn't the best tracker in the world. Once we had a solid lock, the uP reduced the loop bandwidth from roughly 5 to about 1 KHz to reduce jitter, which made it even easier to kick out of lock. This is for the NIF laser, running megabucks per shot, so I didn't want to ignore the problem.
John
The lengths some people will go to perpetuate their lies...is this some kind of stock option scam on Vectron?
In article , Pooh Bear wrote: [...]
The bipolar ones are often the worst way to go. Using two polar ones and applying a large pre-bias works better.
Lots of folks have worn them their entire lives. I've noticed how valuable they are as safety glasses. A squirt of grapefruit juice headed towards my eyes? No problem. Snip a component lead and a bit of metal goes flying? No problem. Holding a knife, point up, and reach up to scratch your forehead? No problem. Stoking the fireplace and a spark heads toward your face, no problem.
In article , Pooh Bear wrote: [... me ..]
Yes.
I assume that 100mV is under 10% of the DC component and well under the rating.
I'd worry about a capacitor rated for 5.6V with 100mV on it.
All electrical-grade copper is OFC.
John
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caps.
non-linearity and should
No, it doesn't exaggerate their non-linearity. Non linerity effects simply can't be reduced there, but no they can't be amplified.
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